1. Field of the Invention
The present invention relates to a pressing apparatus, and more particularly, to a pressing apparatus for de-watering a continuous web, such as a paper web.
2. Description of the Related Art
A paper making-machine is used for making a fiber web, or continuous web, from a fiber slurry. The fiber slurry is typically in the form of fibers, such as wood fibers, which are suspended in water. The fiber slurry is introduced into a headbox. The function of the headbox is to convert the slurry into a highly uniform flat jet of liquid, which is drained on forming fabric, which creates the fiber (paper) web. In order for a uniform sheet of paper, it is desired to create a highly turbulent flow area within the headbox in order to break up flocks in the slurry. In general, the higher the turbulence, the smaller the flocks, and thus, the more uniform the sheet of paper. The draining also effects the quality of the sheet, and the size and cost of the machine.
Accordingly, a need exists for an improved apparatus and method for forming a fiber web, such as a paper web. on a forming fabric.
The present invention is directed to an apparatus and method for forming a fiber web, such as a paper web, on a forming fabric in a pressurized chamber.
One aspect of the invention is directed to an apparatus for making paper using a forming fabric. A plurality of rollers are arranged for cooperative rotation, each of the plurality of rollers having a first circular end, a second circular end and a cylindrical middle surface. The plurality of rollers are positioned to define a corresponding plurality of nips, the forming fabric being processed through at least two of the plurality of nips. and at least a first roller of the plurality of rollers having at least one void formed in the cylindrical middle surface. First and second sealing panels engage the first and second circular ends of each of the plurality of rollers. The first and second sealing panels and the plurality of rollers define a chamber. A conduit is positioned in the chamber and has a plurality of distribution holes extending across a width of the forming fabric. A pressure source is fluidly coupled to the distribution conduit to supply a pressurized flow of a slurry in the chamber across a width of the forming fabric to form a continuous web. The continuous web is formed on the forming fabric at a location in the chamber where the chamber fluidly communicates with the at least one void formed in the cylindrical middle surface
Another aspect of the invention is directed to a method of forming a continuous web on a forming fabric, comprising the steps of providing a pressurized chamber; processing the forming fabric through the pressurized chamber; and distributing a pressurized flow of a slurry having a first composition in the pressurized chamber across the width of the forming fabric to form the continuous web.
An advantage of the present invention is that the forming area can be shortened over that of a typical headbox arrangement, and the forming area can be controlled by the application of pressure within the chamber.
Another advantage is that the present invention can be joined seamlessly with a cluster press, such as the multi-roller arrangement shown in FIG. 1, as to form a compact paper machine.
Another advantage is that the present invention can incorporate multiple chambers to form multi-ply paper, to successively form a first layer of a first material, de-water it, and form a subsequent layer in a subsequent chamber out of a second material.
Yet another advantage of the present invention is that the continuous web is formed on a forming fabric in a closed pressurized chamber, thereby reducing the possibility of contamination at the early stages of the continuous web (fiber web) forming process.